Dynamically tunable photonic spin Hall effect based on insulating-metallic phase transition of Vanadium Dioxide

Abstract

The photonic spin Hall effect (PSHE) can manifest as the spin-dependent splitting (perpendicular to the plane of incidence) of a light beam, i.e., transverse beam shift. Introducing dynamically tunable PSHE into post-fabricated systems has great potential for the new type of photonic devices and its tuning range can be manipulated with different reconfigurable methods. Most of these methods are based on modifying the refractive index of bulk or interface materials. However, the perturbation on the refractive index is usually small, leading to difficulty in enhancing PSHE. Fortunately, the changes in the refractive index of Vanadium Dioxide (VO2) with insulating-metallic phase transition can be larger in several orders than that of other materials, making it possible for enhancing PSHE to have greater tuning range. Here, to explore the dynamically tunable PSHE based on the insulating-metallic phase transition of VO2, the transverse beam shift (as an indicator of PSHE) was calculated with a full wave theory at a wavelength of 1550 nm in a layered structure. Without a gold layer, only the PSHE of the H-polarized beam shows significant tunability in the insulating-metallic phase transition of VO2. With the Au layer, the PSHE of the H- and V-polarized beam is enhanced around the Brewster and Brewster-like (originating from the destructive interference between the nanosized layers) angle, respectively. For H- and V-polarized beams, the tuning range of PSHE is mainly determined by the insulating phase of VO2 and can be enhanced with the Au layer. Finally, as an example, the enhanced tuning range makes the output of a two-digit binary code conversion based on PSHE easier to recognize. These results offer us possible ways to control the tuning range of PSHE in post-fabricated systems and provide more potential for new applications.